1. Technical Field
Embodiments of the present invention relate generally to cryosurgical equipment, and, more particularly, to the heating and cooling of cryoprobes or cryocatheters.
2. Description of Related Art
Cryoprobes that utilize a change of phase of a fluid cryogen, when this liquid cryogen is supplied from an external source into the cryoprobe tip, are known for performing cryosurgical procedures. Generally, a cryogen is delivered into a cryoprobe in the form of either a liquid and or two-phase fluid. The liquid phase of the delivered cryogen then cools the tip (distal section of the cryoprobe), by total or partial evaporation.
It can be advantageous to be able to both heat and cool the cryoprobe, in order to increase the efficacy of ablation. Most cryoablation treatments feature two cycles of cooling, separated by a thawing cycle, for increased efficacy, because the greatest damage to the tissue occurs during either a rapid decrease or a rapid increase in temperature, when the tissue goes through a phase change. A heating cycle therefore improves this phenomenon during thawing. The need for heating at the end of the treatment is twofold, the rapid heating improves the efficiency of the treatment, and the probe can be easily released from the tissue shortening the total procedure time.
Some compressed gases, such as helium, heat upon expansion. That is why helium is extensively used in Joules-Thomson processes.
U.S. Patent Publication No. 20060122590 discloses a device for both heating and cooling a cryoprobe, using a single source of gas, in Joules-Thomson process. This device, however, is based on the use of adiabatic expansion of high pressure Argon for cooling, and reducing the high pressure to reduce this cooling phenomenon to a minimum and heating the low pressure Argon.